74 Working v. Fighting. [December, 
appears not merely an intermixture in varied proportions of 
the parental attributes, but the latter are rendered unstable 
or mobile, and the young become more easily modified by the 
conditions in which they are placed. A splendid field tor 
experimental research is here opened. 
Mr. Wallace does not discuss hybridism and its conse- 
quences. But he holds that species are not all and at all 
times equally variable, and he shows reasons for assuming 
that the present condition of the earth is one of exceptional 
stability as to climate, and consequently of exceptional 
stability of species. It need scarcely be said that these con- 
siderations supply the solution of certain serious difficulties. 
They meet the objeaion of the almost infinite lapse of time 
required for the evolution of species, if its rate is supposed 
to be constant : they answer— if any answer is needed— the 
cavil that none of us have witnessed the evolution of a new 
species, and they will surely satisfy those “ eingefleischte 
anti-Darwinianer ” who still cling to the “Egyptian 
fallacy.* It is remarkable that the the climatic conditions 
of Egypt have probably undergone less modification during 
the past three thousand years than those of most other 
countries. If, then, its present animals are exaftly similar 
to those found as mummies or depicted on its monuments, 
the fadt is in accordance with, and not in opposition to, the 
dodtrine of Evolution. . . , 
Prof. Semper gives a much-needed caution against the too 
common error of arguing from the position of an animal in 
the zoological series and from the structure of its organs, 
e a its dentition, to its habits and its selection of food. 
The well-known pond-snail, Lymnceus stagnalis, belongs not 
merely to a herbivorous group of snails, but its teeth are 
formed on the true plant-eating type. Yet it attacks and 
devours the small water-newt, Tviton tcsmatus, even in an 
aquarium full of flourishing water-plants. The present 
writer has seen the same species feasting on frog spawn, 
though there was at hand vegetable food in abundance. 
Some of the rodents are purely vegetarian ; others, with 
similar dentition, are semi-carnivorous, like the rat or the 
squirrel, which the author very corredtly pronounces the 
greatest enemy of our song birds, whose eggs and young it 
devours in great numbers”! . 
He holds that “ by far the greater number of animals 
• Journal of Science, 1880, p. 166. . , , . . 
t As this marauder has also a decided taste for wall-fruit he ought to be 
extirpated wherever practicable. 
